1. Field of the Invention
The present invention relates to a vehicular power source unit having a fuel cell.
2. Description of the Related Art
Conventionally, there has been known a vehicular power source unit (for example, refer to Japanese Patent Laid-open No. 2005-317410) which is provided with a fuel cell and an auxiliary power source (a battery, a capacitor or the like) and is configured to operate a heater to heat the fuel cell with the electric power supplied from the auxiliary power source at a low temperature.
In the conventional vehicular power source unit, after a given time interval has elapsed from the halt of a vehicle, the hydrogen in the fuel cell is scavenged and power generation from the fuel cell is suspended. In this case, when the hydrogen is supplied to the fuel cell to restart the power generation from the fuel cell, it will take some time to raise the voltage generated from the fuel cell until stable.
Moreover, if the power generation from the fuel cell is restarted at a low temperature, it will take additional time to raise the temperature of the fuel cell to an appropriate temperature. Therefore, the time needed to raise the voltage generated from the fuel cell until stable will become further longer.
If the vehicle is started before the temperature of the fuel cell has been sufficiently raised, the electric current supplied from the fuel cell will become greater, which in turn decrease the voltage generated from the fuel cell drastically. Consequently, the component materials of the fuel cell are deteriorated, which degrades the performance of the fuel cell.
Thus, before the generated voltage from the fuel cell is raised until stable, it is required to assist the fuel cell with electric power supplied from the auxiliary power source to run the vehicle. However, in this case, if an amount of charge of the auxiliary power source is insufficient, the fuel cell may not be sufficiently assisted by the auxiliary power source, which leads to a problem that it will take a longer time for the total power output from the fuel cell and the auxiliary power source to reach a level required to run the vehicle.